|Observation data (2000 epoch)|
|Right ascension||18h 08m 39.33s|
|Declination||−20° 24′ 40.0″|
|Distance||~50000 ly (~15000 pc)|
|Notable features||Contains SGR 1806-20 and LBV 1806-20.|
|Other designations||G10.0-0.3, W31|
|See also: Open cluster, List of open clusters|
Cl* 1806-20 is a heavily-obscured star cluster on the far side of the Milky Way Galaxy, approximately 50,000 light years distant. It contains the Soft Gamma-Ray Repeater SGR 1806-20 and the luminous blue variable hypergiant star LBV 1806-20, a candidate for the most luminous star in the Galaxy. LBV 1806-20 and many of the other massive stars in the cluster are believed likely to end as supernovas in a few million years, leaving only neutron stars or black holes as remnants.
The cluster is heavily obscured by intervening dust, and mostly visible in the infrared. It is part of the larger W31 H II region and giant molecular cloud. It has a compact core (diam ~0.2 pc) with a more extended halo (diam ~2 pc) containing the LBV, and also contains at least three Wolf-Rayet stars (of types WC8, WN6, and WN7) and an OB supergiant, plus other young massive stars.
- SIMBAD/Aladin plot, of r=30 asec region around SGR B18054117-20251165
- D. F. Figer et al. Astrophys.J. 622 (2005) L49-L52
- The Unusual High-Mass Star Cluster 1806-20 
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